Would it be possible to have a simpler registration with merely the basics?
The problem seems to be that the registration don't pass, there is an error on the password or some other field. Can the password field be saved, so you don't have to re-enter it?

The "forum rules" is also translated; this make changes difficult if you wish to use something else. How about 2-3 different "standard" forum rules, a friendly one, a strict one, a short with a reference to "forum rules", that admin can set up as an ordinary post.

The registration process is a bit intimidating. However, I don't think it is good practice to save the password. We should actually use AJAX call-outs to validate information as it is typed into the form.

W.r.t. the "forum rules": You don't have to use the translated messages. You can simply edit the template file (pre_reg.tmpl) and enter your own verbiage into it.